The union membership rate fell from 11.8 percent to 11.3 percent of all workers, the lowest level since the 1930s.

Total membership fell by about 400,000 workers to 14.4 million. More than half the loss — about 234,000 — came from government workers including teachers, firefighters and public administrators.

The losses add another blow to a labor movement already stretched thin by fighting efforts in states like Wisconsin, Indiana and Michigan to curb bargaining rights and weaken union clout.

But unions also saw losses in the private sector, even as the economy expanded modestly. That rate fell of membership fell from 6.9 percent to 6.6 percent, a troubling sign for the future of organized labor, as job growth has generally taken place at nonunion firms.